In video signal processing it is now well-known to use a digital store capable of storing at least one picture (two fields of an interlaced signal), so that special effects can be produced by operating on the information contained in the store. As a simple example the effect of a "zoom" can be achieved by increasing the apparent size of the stored image, or a "pan" or side-by-side motion can be achieved by simulating sideways movement of the camera.
Such digital effects simulators are very expensive. They also suffer from the disadvantage, particularly on a zoom for example, that as the apparent size of the image is blown up the resolution or quality of the picture goes down. For example if the effect of a zoom down to one quarter of the original picture area is required, then the information which previously related to one pixel (picture element) now has to be spread over four pixels. In practice the situation can be much worse than this.
I have appreciated that there is one particular situation where the effects produced by a digital effects simulator can be obtained without the cost of a digital picture store and without this degradation of quality. This situation is where (a) the original image is a still image held on a slide or a single frame of cinematographic film, and (b) the video signal is produced from the image by means of a telecine.
A telecine is a known piece of equipment which is designed to produce TELEvision signals from CINEmatographic film, and is commonly used by television stations and the like to provide television signals from feature films or from news material recorded on film. Such apparatus is therefore in existence in broadcasting stations, and I have realised that a relatively-speaking inexpensive piece of additional equipment can be used to give the same effect as a digital effects simulator costing some tens of thousands of dollars.
There are basically three known types of telecine, namely flying spot, camera tube, and solid state array (usually linear array) telecines. In a flying spot telecine, the film runs between a cathode ray tube operating as a light source and a simple lightsensitive detector. The cathode ray tube is arranged to display a single spot of light which follows a raster such as to scan the film with the desired scan pattern, and the detector output thus forms the basis of a television signal. The less-common camera tube type is in a sense the converse of this, as the whole film frame is illuminated by a light source, opposed to which is a camera tube which operates with an appropriate scanning raster but otherwise like any other television camera to provide a scanned output. So far as solid state array types are concerned, only linear array types are on the market and in these the film runs between a light source and a linear semiconductor light sensor arranged across the film path on the other side of the film. Typically the sensor will have 1024 individual elements or cells. Thus one line is sensed at a time, and the array is emptied as though it were a shift register to provide a signal representing one line. Two-dimensional arrays can be foreseen in which more than one line might be available simultaneously.
Telecine systems generally preferably run with the film in continuous motion rather than in intermittent motion as in a cine projector. The movement of the film during scanning is compensated in well-known manner by appropriate distortion of the scanning raster. The telecines can be controlled by remote user controls which allow various functions to be executed, for example, slow replay, inching forward, reversing and also selecting part only of the image from the cine film, particularly where it is a wide format film such as a cinemascope film, when only a part of the image having the same aspect ratio as a television picture can be selected for transmission as a video signal.
It is known to use a pre-programming system with telecine equipment and one example of such a system is that sold by Rank Cintel Limited of Ware, Hertfordshire, England under the trade mark AMIGO. This pre-programming system is designed for use in recording a feature film on videotape for subsequent broadcasting, and is basically intended for use with flying-spot telecines. The colours on feature films, particularly older ones, are not particularly accurate, and it is therefore desirable to adjust the colour rendering to give a subjectively satisfactory appearance when viewed on a television monitor. The AMIGO pre-programming system thus allows an operator to correct the colours and indeed to store the necessary corrections so that they are applied at the required points in the running of the film. To locate the correct point it counts film frames as the film runs through the telecine. The system is also capable of interfacing with the telecine user controls so that for example with a cinemascope film the desired preprogrammed portion of the image is selected for transmission. This information is recorded in the system in relation to specific film frames by counting cine film frames from the beginning of the film.